if I make a plan which causes the project to be identical to its state 5 years ago, the edit distance is zero, but in no way can you call that a measure of history
You're still thinking in graphs. That plan would already exist in the database, you would just be making it a build target instead of whatever new plan was targeted before.
It seems as though you've come up with a model for representing source code repos in terms of a data model of your own design, solving problems of your own choosing. But what you describe is not a version control system in the generally agreed upon sense of the word.
